1. Field of the Invention
This invention relates a molded plastic wheel and, in particular, to a single-piece, hollow-form, integral wheel for use on bicycles.
2. Brief Statement of the Prior Art
Plastic wheels for bicycles and other applications have been provided by a variety of molding techniques. A large number of prior patents disclose wheels which are made by injection molding, but which are not hollow-form. Instead, these wheels have solid ribs or spokes which extend between a central hub and outer rim. Examples of such patents are U.S. Pat. Nos. 4,508,392 and 4,793,659. Other attempts to provide a molded plastic wheel suitable for use on bicycles are described in U.S. Pat. Nos. 3,862,779 and 4,818,034. In these patents a hollow-form wheel is assembled from split, mirror image halves and the assembly is retained by suitable fasteners or studs. While this approach can provide a hollow form wheel, it compromises the strength of the wheel and requires substantial manual assembly.
Another attempt to provide a plastic bicycle wheel is disclosed in U.S. Pat. No. 4,844,552. This patent describes a spokeless wheel having a solid center which is formed by an assembly of annular diaphragms between a central hub and outer rim. Although not patented, a molded plastic bicycle wheel has been marketed with limited success. This wheel is a three-spoke plastic wheel which is made by applying multiple layers of resin impregnated graphite fiber onto a rubber mandrel that is placed in a mold and heated to cure the resin. Thereafter, the rubber mandrel is extracted from the hub area of the wheel and a separate rim and a separate hub are bonded to the wheel by secondary bonding. This procedure is very tedious and relies substantially on custom hand fabrication. It does not provide the precision and accuracy that is desirable for consistent performance in quality of the wheel, and the strength of the wheel is lessened by the requirement that the rim and hub are not integrally formed.